The 18W USB-C power adapter shipped in the box with the iPhone 11 Pro. Then, in October 2020, Apple quietly replaced it with a 20W USB-C power adapter — sold, like its predecessor, for $19. If you’re holding one of these little white bricks and wondering whether the extra 2 watts matter, or whether you bought the wrong adapter, here’s the real difference.
The short answer: for wired charging, almost nothing changes. The one place the 20W adapter actually matters is MagSafe.
How to tell which adapter you have
The two bricks look nearly identical, so check the fine print on the side: it reads either “18W” or “20W” USB-C Power Adapter. If yours came in the box with an iPhone 11 Pro, it’s the 18W model; anything Apple has sold since October 2020 is the 20W model.
For wired charging, the difference is negligible
Both adapters use USB-C Power Delivery, and both charge an iPhone over a USB-C cable at effectively the same speed — roughly 50% in about 30 minutes for recent iPhones. A 2-watt gap at these power levels doesn’t translate into a meaningful time saving on a full charge. So if you charge with a cable, the 18W and 20W bricks are interchangeable in everyday use. (Both will also happily top up an iPad; see our guide to fast charging an iPad for which adapter suits larger devices.)
The real difference: MagSafe at full 15W
Where the 20W adapter earns its keep is MagSafe wireless charging. Apple’s MagSafe charger can deliver up to 15W to a compatible iPhone — but only when it’s paired with a 20W or higher USB-C adapter. Plug a MagSafe charger into the older 18W brick and wireless charging runs slower, because the 18W adapter can’t feed the puck its full 15W. If you use MagSafe daily, the 20W brick is worth having. While you’re at it, make sure your gear is the real thing — here’s how to check if a MagSafe charger is genuine.
So did you buy the wrong adapter?
Almost certainly not. Apple priced the 20W model at the same $19 as the 18W one, so nobody overpaid — and unless you charge with MagSafe at full speed, you’ll never notice which brick you’re using. The only case for specifically buying the 20W adapter is MagSafe at 15W. For everything else, including topping up bigger devices occasionally (though a MacBook charges best with a higher-wattage brick — see MacBook Pro fast charge adapters), either adapter does the job.
If it still doesn’t work
If your iPhone charges slowly with either adapter, try a different USB-C cable first — cheap or worn cables are the most common bottleneck. Check the charging port for lint, and try another wall outlet. If your iPhone stops charging at 80%, that’s not a faulty adapter: it’s Optimized Battery Charging, which you can read about in our guide on why an iPhone won’t charge past 80 percent.
FAQ
Can the 20W adapter damage an older iPhone?
No. USB-C Power Delivery negotiates power with the phone, which draws only what it needs. Using a 20W adapter with an older iPhone is completely safe.
Should I replace my 18W adapter with the 20W one?
Only if you charge with MagSafe and want the full 15W wireless speed. For wired charging, keep your 18W brick — it performs the same in practice.
Wrapping up
The 18W vs 20W question has a simple answer: they’re the same adapter in every way that matters for wired charging, and the 20W version exists mainly to unlock MagSafe’s full 15W. If you bought the 18W one back in the day, you didn’t buy the wrong adapter — unless MagSafe speed is your priority.
